<p><it>Abstract</it>—Over the past few years, the topic of active databases has become an important area of research. A number of efforts—both research prototypes and commercial database management systems (DBMSs)—have addressed support for event-condition-action (ECA) rule in databases. This paper examines the motivations for providing this capability, identifies features that form the basis for supporting active functionality and provides a capsule summary of active database features of early commercial systems as well as research prototypes. Three broad categories—rule expressiveness, execution semantics, and efficiency—are used for the capsule summary.</p>